摘要(英) |
Both
numerical analyses and field tests were accomplished to study
the anchorage behavior of underreamed anchor groups in silty
sand. A series of triaxial tests were performed on specimens
taken from test site, based on the constitutive model of
cohesionless soil named SHASOVOD (A continuous strain hardening-
softening and volumetric dilatancy model), to obtained the
parameters needed for the model. The model and the parameters
were then quoted to evolve a numerical program by FORTRAN
language, along with FLAC3D software to analyze behaviors of
single anchors and anchor groups in silty sand. In addition, to
verify the suitability of the numerical program, filed tests on
a single underreamed anchors and an anchor group arranged in 2*2
matrix were conducted in silty sand. After the calibration, a
succession of parameteric analyses was carried out to study the
anchorage behaviors of single underreamed anchors and anchor
groups in silty sand.
It can be seen from the results of field test, an ultimate load
of 650kN was estimated meanwhile the anchor head displacement
reached 11cm for a single anchor with diameter of 40cm, free
length of 10m, and fixed length of 5m; On the other hand the
ultimate load of 610kN was measured with respect to the average
of anchor head displacement of 9.4cm for a 2*2 anchor group with
spacing of 160cm. Therefore, efficiency of an anchor group was
computed to be 94%.
It can be seen from the numerical results of 2 by 2
matrix-arranged anchors, no matter which it changes the fixed
length or overburden depth, when the anchors were spaced was
more than 7.5 times of anchor diameter D, it can eliminate the
influence of anchorage capacity. Yield zone of soil develops to
ground surface and it occurs superposition, when overburden
depth of 5D and horizontal space of 2.5D (1m). The superposition
of yielding zones will not be able to occur and the yield zone
of soil will not develop to the surface when the anchors apart
were spaced more then 5 D apart horizontally. Meanwhile, it can
be found from the numerical results, the efficiency of 3*3
anchor group is greater than that of 2*2 anchor group. |